Retinometer



E. P. COOK July 11, 1933.

RETINOMETER Filed Feb. 5, 1951 2 SheetS-Sheeb mnmwl E. P. COOK RETINOMETER .uly 11, 1933.

Filed Feb. 5, 1931 `2 Sheets-Sheet 2 Patented July l1, 1933 stares 1 teasers l n Wil dell a l s musee ERNEST P. COOK, OI BERLIN, NEW HAMPSHIRE RETINOMETER Applicateu filed February 5, 1931. Sera1 No.v513,569.

This invention relates kto apparatus for practicing the method of retinoscopy in determining the refraction of the human eye.

Retinoscopy is one of the most useful and f accurate methods known for measuring the refraction ofthe eye so as to provide correcting` -lenses therefor. Briefly, the method consists of reiiecting a beam of light from a v nearby hooded lamp into the eye of the patient by means of a small mirror in such a yay that the light is reflected back to the mirror from the interior of the eye andthe emergentrays are observed through a small A hole in the center of the mirror, this hole being preferably in the silvering only of the mirror and not extending through the glass.

t is an object of this method, as customarily practiced, to place inV front ofthe observed 1 eye ancutralizing lens adapted to lconverge the emergent rays and to bring them to a focus at a finite distance from the eye. In the case of all eyes, except strongly myopie eyes, the neutralizing lens must be convex.

lt is obvious that the stronger the neutraliz- L'" ing lens, thenearer to the eye Will `be the `focal pointof the emerging rays. Instead of moving toward or away from the patient in order to locate by observation 'the .focal point or point of reversal of rays emerging from an eye combined With a neutralizing lens, it is convenient to adopt a iixed position of observation and to use in succession neutralizing lenses of different strengthsso r that Va lens can be discoveredA With which the eye will have apoint of reversal at ornear the point of observation. For this purpose it is convenient to adopt a distance of one meter from the eye of the patient, since this A means an allowance-of one diopter in estimating the refraction of the patients eye from the strength of the neutralizinglens. A smaller distanceof observationcanlbe used, but theV limits of possible error increase greatly as the distance of observation is dii minished. As customarily practiced, this method of retinoscopy involves the use 0f a. trial frame which is Worn by the patient, the observer placing in'this frame the successive neutralizing lenses. After4 each lens is placed in the frame, the observer holds his Ilz.

mirror to direct the beam of light toward the pupil of theppatients eye and observes the reflected rays through the peep hole.

In order to determine both the character of the refraction of the observed eye and the approximate location of the'point of reversal, the mirror is tilted Vslightly back and forth on a` vertical axis to cause the spot of light on the patients face to move back` and forth horizontaly. lf the point of ,reversal is behind (i. e. beyond) the mirror, the area of' lightrellected from the pupil of the eye appears to move back and forth laterally with the spot of light on the patients face sur-v rounding ythe eye. lf 'the point of reversal is between the observed eye Vand the mirror, the light from the pupil .of .the eye appearsv to move laterally in a direction opposite to the motion of the light on the face. lWhen the neutralizing lens is such that the point of reversal is substantially coincident With'the position ofthe mirror, there is no observable motion of thelight in the pupil of the eye when the mirror is tilted. rlhus the practice of retinoscopy ordinarily involves the frequenty changing of lenses in thev trial frame Worn by the patient and a ti ting back and forth of the observers mirror after each new lens is inserted. Frequently a` considerable number, six or more, Vlenses required before the refractive properties of an 'eye can be determined. In the case of astigmatism, a larger number ofneutralizing lenses may have to be employerhas it is necessary to nieasurethe refraction of the eye on both of the principal meridiane. lf, as is custo# mary., the observer isV at a distance of about.

one'meter from the'patient, the changing of l neutralizing. lenses. involves` leaning forward and reaching out atV arins length to remove a lens from the'trial frame and to substitute another. This and the frequent tilting of the mirror involve in the, aggregate a great deal of monotonous and fatiguing exertion whichl tires the observer and in time tends to diminish his powers of accurate perception. The exertiony incident kto the use of several neutralizing lenses Vin succession also temptsv an observer, particularly Atoward the end of a day when he isliable to be tired, to curtail the examination by relying on his judgment based on a few observations rather thanto check up thoroughly by trying additional neutralizinglenses. This involves danger of incorrect determination of the condition of the eye observed.

It is an object of the present invention to provide mechanism by which practically all of the fatiguing movements now made by the observer are mechanically performed. .The various controls for the neutralizing lenses, the tilting of the mirror, and the adjustment of the apparatus made necessary by the presence of astigmatism in the observed eye are all conveniently at hand, as well as a scale for indicating the strength of the neutralizing lens in operating position at any moment. By the use of a mechanism as hereinaftei described, not only is the observer Asaved a great deal of fat-iguing exertion, but the.' distance of observation is accurately maintained and the motions are correctly performed. This aids in the more accurate and careful determination of the refractive properties of the observed eye.

Various other advantageous features will be apparent to one skilled in the art from the disclosure `in the following description and in the illustrations of the drawings, of whicln- Figure l is an elevation of an 'apparatus embodying the invention.

Figure 2 is a longitudinal section of the main portion of the apparatus showing most l of theA working parts.

Figure is an end elevation of the apparatus shown in Figure 2, from the point of view of the patient.

Figure 4 is an end elevation of the apparatus at the observed end.

Figure 5 is an elevation of the dials illustrated in Figure 4, showing the scale markings which may be employed.

Figures 6 and 7 are fragmentary portions of a horizontal section of the apparatus taken on the line 67 of Figure 2.

Figure 8 isa section on the line 8-8 of Figure (i.

Figure 9 is a section on th-e line 9--9 of Figure 7.

Figure l() is a section on the line lO-l() of Figure 7. Y

Referring to Figure l, the retinometer is for the most part included in an elongated housing which is suitably mounted on a tripod standard 21, and, if desired, it is vertically adjustable thereon. This standard may also carry a suitable chin rest 22 and cheek rest 23. The housing 2O is preferably one meter in length and may have any c0nvenient cross sectional shape, such as those shown in Figures 8 and 9. For convenient access to the interior, the housing may be formed in two pieces which may be hinged together as at 24.V As farV as possible all the surfaces within the casing 2O are finished in dull black to avoid undesirable and confusing reflections.v Extending downwardly from the cover portion of the housing is a lam-p box 25 havingan aperture 26 therein on the side toward the observers end of the housing. This lamp box is cylindrical and contains an inner box 27 rotatable therein. The inner box may be provided with two or more lateral apertures of varying size. As shown, two apertures 28 and 29 are provided, either of these apertures being brought into registry with the aperture 26 by manual rotation of the inner lamp box 27. Thus the opening for theV light beam may be large or small as desiredand maybe readily changed by rotating the inner lamp box 27. lVit-hin the box 27 is mounted a suitable elec tric light SO.- By projecting the lamp box downwardly into the'interior of the housing, the lamp is brought as closely as possible into line with the eye of the observer. so that the angle of reflection of the light bram is thus as small as possible. The beam from the lamp vis caught by a suitable retinoscopic mirror which is mounted on an end wall 36 of the housing, this wallv being slightly` tilted so thatthe mirror which is mounted with its plane parallel to the plane of the end wall 36 will reiiect the beam of light directly intoV a sight hole or aperture 37 in the opposite end wall of the housing. The mirror is mounted within a ring 38 byV a pair of pivots 40 which are diamet-rically opposed. As shown in Figure 4, these pivots may provide a vertical rocking axis for the mirror 35. A rocking motion may be imparted to the mirror as by an edge cam 4l on which ride a pair of ears 42 extending .from the .rim of the mirror at points preforably ninety degrees from the pivots 40. The edge cam 4l may be on a gear ring 43 which maybe rotated by a pinion 44. This pinion may be driven through a 'liexible shaft 4.5 and reducing gearing 4.6 by a suitable electric motor 47.. A treadle 48 may be provided for the convenient control of the motor.v this treadle operating a suitable rhcostat by which the motor mav be rotated at any desired speed. Thus by pressing the trcadle 48, the mirror 35 may be'tilted'baclr and forth through the correct angle Jfor the purs pose, on an accurate vertical axis, and with practically no exertion on the part of the operator.. The mirror 35may have a suitable peep hole 50 made by removing a small central portion of the silvering. As most observers naturally use the right eye in sighting through the mirror, the mirror is preferably'mounted in a position convenient to the right eye, a simple aperture 5l being left in the end wallof the housing for theV left eye.

A set of neutralizing lenses may be mounted in successive frames 56 which may consequent shitting ofthe lenses.

be hinged together as shown, forming a chain. Each lens may be carried in an individual rine 57- suspended by three.A or more tine Wires 58 Within a somewhat larger circular opening through a square frame 56. This clearance between the rings 57 and the frames 56 is lett so to permit observation of a diametrical white band 60 on' an axometer disk 61.- This axometer may have a central perforation registering with. the opening 37, and may bc rotatable about its cent-er as an axis to move the White band 60 in line with any observed axisot astigmatism in the patients eye. The frames 56 are hinged together at their upper and lower corners as shown in Figure 2, leaving an .aperture 62 between each pair of successivev trames.

These apertures are adapted to -rcceive the teeth 63 of a suitable sprocket kWheel 6l which is preferably substantially square and which carries tour teeth 63. -By rotation of the sprocket 1vheel 614;, therneutralizing lenses are moved successively in front ot and in line with the aperture ,37. In order to insure proper and accurate registry ot a lens With this aperture? the sprocket Wheel 64 is mounted on a shortshatt 65 which is movable in av slotted trame 66 toward orfrom the aperture 37. Y A spring 6711s carried by the trame 66 and presses the sprocket Wheel to-V corner of the. sprocket Wheel bears aga-inst-V the end Wall of the housing. After the Wheel has been turned more than 45, the action ot the spring helps to turn it to bring the next successive side edge ot the Wall flat against the end Wall ot the housing, in which position the next neutralizing lens is accurately positioned in line with the aperture B7.

The sprocket Wheel-64 may be actuated l` through a flexible shatt- 68 and a shaft 70 extending to the opposite end of the housing. lilounted on the shaft 70 is a. fingerV Wheel 71 which may be suitably knurled to facilitate the rotation ot the sprocket Wheel and the The tin-V ger Wheel 7l, being located at the observers end of the apparatus, is convenient` l'or ma# nipulation. Thevends ot' the chain of lenses 1u ay be connected by ay pair Vot suitable cords ortlexible Wires 72 through suitable s rings 7 adapted to take up any slack inthe closed loop thus formed. These cords or Wiresmay extend around suitable idlepulleys 74.` A-

i air. of elongated screens 75 ma be mounted l' Within the housing, these screens being lmetal prevent any objectionable .shaftl v70 also'carries a initer gear 8O Which meshesvwith a gear 8l on a lshort shaft 82. Thiscarries a second gear 83 which meshes With a-ring 84 which ismounted on the end Wall 36 of the housing to rotate in its plano about itsceni'zer,V and which carries a series of tc'ethadjacentto its ri 1n. The ring 84 thus rotates When-the rshaft 70 rotates. This ring may be provided with suitable scaleV markings, as shovvnrin Figure 5, thevscale markings being sospaced as to correspond to the strength of the neutralizing lenses which are successively moved into line with the aper-V ture 37. f` These lenses may conveniently differ successively in strengthby one hall diopter, the scale being soV arranged that when Vthe, shaft 70 is rotated sufficiently to turn the sprocket Wheel 64- thro'ugh an angle of 90, that is, to replace one neutralizing lens with the next-successive neutralizing lens in vline With the aperture 37, the scale 'bearingf ring 84 rotates a distance equivalent to one halt ydiopter on the scale. An index 85 may be provided to indicate the ,strength of the lens in position at any time. This index is carried by aring 86 which is concentric With the ring 84h As the apparatus is used to best advantage in Va. dark room, Inlay mount a small Vlight on the casing 4to illuminatethe scale. The light may be a small electric bulb mounted inra suitable box and covered by a hood 87 Whichmay have a lateral'opening 88 and maybe manually rotatableto move the opening 88 into or out of vregistry with a similar opening in the box Within the hood. Thus the light may readily be turned on the scale When desired. t Y

As is usually desirable to use neutralizing lenses differing by one quarter diopter,v I have provided an auxiliary lens 90 of one-quarterA diopter power Which can be swung down in line with the aperture 37 so as to modify the strength of 'the neutralizing lens in line with the aperture. 37; Thus, or'exampleyif the neutralizing lens is plus 2 D., the laddition ot the lens 90V makes an effective 'neutralizing lens of plus 2.25 D. -The lens 90 may be mounted on a suitablebellcrank 9i connected through a rod 92 to a crank'arm'98 vvhchlis mounted on a sleeve 94 surrounding the shaft 70. Mountedalso on the sleeve 94 is a finger Wheel 95 by manipulation of which the lens 90 may bemoved'into or out of line with the aperture Thepresence or absenceo" the rio lens 9() before the aierture 87 ma be automatically indicated on the scale of the .ringA the bell crank 98-100 is rocked so as to shiftv the index one V.scale division (equivalent to 0.25 D.) lvtoward the right, as in Figure 5. This indicates on the scale an increase of one quarter diopeter in the strength of the neutralizing lens in line with the aperture 37. In measuring the refraction of an eye on the horizontal meridian, the observer starts with no neutralizing lens before the aperture 37. Vhen the patient is in positionl with a pupil of his eye alined with the aperture 37, the observer looks through the peep hole 5 0 in the mirror and observes the nature of the reflection from the eye of the patient. The treadle 48 may then Vbe pressed to rock the mirror back and forth, causing the beam of light to oscillate from side to side. The character of the retinal illumination and its apparent motion give to the observer a preliminary idea of the character of the observed eye. The linger wheel 71 is then turned to bring a neutralizing lens of desiredv strength into line with the aperture 37, whereupon the mirror is again oscillated and the effect of the oscillation is observed. The neutralizing lens may be readily changed asdesired until the lens of correct strength is found to bring the point of reversal substantially in the plane of the point of observation, the auxiliary lens being employed if the desired strength lies between a whole diopter and the adjacent half. Thus the spherical refractive properties of the eye on a horizontal meridian may be determined with great accuracy. In a large percentage of eyes, however, there is present more or lessastigmatism. Hence the mechanism is designed to facilitate the examination'of eyes on various meridians.

Y yIn cases of pronounced astigmatism, the light reflected from the eye is in the form of a band instead of a'circle, this band of light indicating clearly one of the principal meridians of the astigmatism.V As it is always desirable to measure refraction of the eye on the principal meridians, the' ring 38, in which the mirror 35 is mounted, is adapted to rotate about the center of themirr or so as to incline the axis of tilt of the mirror to be in line with any meridian of theY eye. To facilitate this alignment, the axometer disk 61 which surrounds the aperture 37 is marked with a dialnet-ric white band 60, segments of which extend radially from the central `aperture of the disk. When thereiiected light from ythe eye is in the form of a band, thev disk 61 is rotated until the segments of the white band 60 are in line with the band of light. The

disk 61. is mechanically connected with theV ring 38 so that the rotation ofthe axometer and the rocking axis of the mirror keep in step.` To thisV end the ring 61 `may be provided with gear teeth meshing with a pinion 105, the pinion being connected through a flexible shaft 106 to a shaft 107 which extends tothe observers end of the housing. The shaft 107 carries a miter gear 108 which meshes with a gear 109 on a shaft'110. A finger wheel 111 is also on this shaft as well as amiter gear 112 which meshes with teeth on a ring 113. The ring 113, as shown in Figure 4, isconnected to the ring 38 as by a rigid link 114 which extends across a fixed ring 115. The ring 115, as shown in Figure 5, may be provided with scale divisions indicating degreesl of are from zero to 180. On the movable ring 113 are suitable index marks to cooperate with the scale on the ring 115, three such marks spaced by ninety degrees being shown in Figure 5.vv The gearing connecting the axomet-er 61 with the index ring 113 is so arranged that the ynumber of degrees of i rotation of the axometer and of t-he mirrorsupporting ring 38V is accurately indicated on the scale of the ring 115..

As it is usually desirable to measure the refraction of an astiginatic eye on both its principal meridians, and as the principal meridians are nearly always at right angles to each other, mechanism is provided by which the axometer may be conveniently turned through an exact right Vangle by the sense of touch without having to observe the scale for that purpose. To this end a pinion 120 `is mounted on the shaft 107, this pinion meshing with a gear wheel 121 loosely mounted for rotation about the shaft 122. This shaft extends through a1 supporting collar 123 on theend of a bracket 124, the shaft being splined to the collar 123 to prevent rotation of the shaft. Mounted on one end of shaft is a clamping plate 125, the opposite end of the shaftbeing threaded for a finger nut 126. Loosely mounted on the shaft 122 is a disk 127 which fits in a circular recess in one face of the gear 121. As shown in Figure 10, a spring pressed detent or click 130 is carriedby the disk 127, a spring 131 being employedto press the detent lradially outward. The outer end of the detent 130 is provided with a double bevel adapted to fit into a suitable notch 132 in the wall of the recessin which the disk 127 fits. Ordinarily the disk 127 revolves loosely about the shaft 122 when the gear 121 is rotated. When, however, the axometer is in line with a principal meridian of an astigmatic eye, the finger nutv 126 may be set tight, clamping the friction plate V125 firmly against the disk 127 so as to prevent rotation thereof. Then the finger wheel 111 is then manipulated to turn the axometer, the gear 121 rotates relatively to the disk 127, forcing the detent in wardly as the notch 132 moves out of reg-V istry therewith. The gear connections'beso that when the detent 130 again clicks into the notch 132, the rings 38 and 113 and the a-xometei` 61 have been rotated exactly 90. Since in nearly all cases, the principal meridians of astigmatism areV at right angles to each other, the second principal meridian is thus correctly presented for observation.

The purpose of the three index marks on ring 113 is to enable the observer to read both angles at one time without the necessity of adding or subtracting 90o from one of the angles.

1 Claim: Y

1. Apparatus of the class described comprising `an elongated housing, an axometer ring having a central aperture and a diametric stripe at one endv of said housing, a lamp-box at an intermediate point of said housing, a` ring in the opposite end of the housing, a mirror supported in said ring and rockable on a diameter of its ring as an axis, means for adjustably rotating both said rings in their own planes, and means for rocking said mirror when its ring is in any position oi' adjustment.

2. Apparatus of the class described comprising an axometer disk having a central aperture and a diametrical band, said disk being mounted to rotate in its own plane about its center, a. retinoscopic mirror mounted at a iixed distance from said disk, means for rocking said mirror on a substantially vertical axis, means for simultaneously rotating said axometer and the rocking axis of the mirror through equal angles, and means lor indicating the angle of rotation of said axometer and axis.

3. Apparatus of the class described comprising an axometer disk having a central aperture and a diametrical band, said disk being mounted to rotate in its own plane about its center, a retinoscopic mirror mounted at a iixed distance from said disk, means for rocking said mirror on a substantially vertical axis, means for simultaneously rotating said axometer and the rocking axis of said mirror through equal angles, and means for facilitatingthe rotation of said axometer and rocking axis through an exact right angle from any initial position by the sense of touch.

4. Apparatus'of lthe class described com- Y prising an `axometer diskhaving a central aperture and a diametrical band, a neutralizing lens, and means forsupporting said lens in operative position in line with said aperture, said means'including a plate having a circular aperture larger than the lens, and a plurality of filaments supporting said lens concentrically in said aperture and substantially inthe plane of said plate, wherebyclearance is maintained around substantially the entire periphery of the lens for observation of the axonometric band Vwhen the lens is in operative position.

5. Apparatus of the class described comprising a series of neutralizing lenses succes-v sively diiiering one-half diopter in strength, movable indicating elements remote from said lensesincluding a scale element and an index element cooperating therewith, means actuable to move said neutralizing lensessuccessively into operative position and` simultaneously to move one of said indicating ele ments a corresponding amount to indicate the Y strength of the lens in operative position, a quarter-diopter auxiliary lens separately movable into and out of operative position inline with the operative position for the other said lenses, and means operatively connecting said auxiliary lens with the other said indicatingelement whereby said other element is shifted when the auxiliary lens isv moved into or out of operative position.

6. Apparatus of the class described, comprising a support, a sighting mirror rockably mounted on said support, an axometer disk mounted at a fixed distance from said mirror, said disk having a central aperture and .a diametrical band and Vrotatable about' its center, a series of corrective lenses carried by said support and movable selectively into line with said aperture, means including a finger piece actuable yto shift lsaid lenses, means including a finger piece actuable to rotate said disk, means in step respectively' with said lenses and said disk for indicating l the strength of lens in line with said aperture and orindicating the angle of rotation of said disk from normal position, said finger pieces and indicating means all being adjacent to said sighting mirror. y

In testimony whereof I have `ailixed my signature.

ERNEST P. COOK. 

